A shattered mum today told how a heartless hoaxer phoned her claiming to have information about the brutal murder of her daughter 23 years ago.

Sharon Henderson broke down in tears as she relived the call, where the mystery man said he was from the Crimewatch TV programme and claimed he had an update into the murder of Nikki Allan.

But the 47-year-old Sunderland mum became suspicious that police had not contacted her regarding new evidence and, when she asked the name of the caller, the phone was put down.

“This has left me devastated,” said Sharon. “Ever since that call came I can’t think of anything else. Why would someone do this?”

For more than two decades, the Sunderland mum has been battling to bring the killer of daughter Nikki to justice.

The seven-year-old vanished after leaving her grandparents’ flat in Wear Garth, East End, on October 7, 1992.

Her shoes were discovered outside the derelict Exchange building a few hundred yards away the next morning. Her body was found inside the building by a neighbour helping police with the search. She had been left lying in a pool of blood. She had been stabbed 37 times in the chest.

Despite police efforts no one has ever been convicted of the murder.

In 2013, 21 years after her killing, the BBC’s Crimewatch programme ran a fresh appeal which reignited public awareness in the case. But, despite millions of viewers tuning in and police trying new DNA testing techniques, the case has remained unsolved.

On Tuesday this week Sharon says she received a call on her mobile phone while at home in Ryhope, Sunderland.

She said: “It was a man’s voice and he said he was from Crimewatch and had some new information about Nikki’s case.

“But as the conversation went on, I started getting suspicious and thought the police would have contacted me direct. When I asked who it was and if they could leave me their number, they just hung up.”

Nikki Allan in her school uniform in 1992

Sharon said the incident was the latest in a series of anonymous calls she has received over the past 12 months which have been abusive and upsetting.

She added: “I can’t take this any more. Why is this happening to me? I’ve kept quiet about it but can’t do it any more.

“After I got that call on Tuesday, I knew I had to call the police.”

Last year, Northumbria Police arrested Sunderland man Steven Grieveson, 47, on suspicion of Nikki’s murder. He was questioned and bailed but detectives later said his bail had been cancelled and he has faced no further current action.

In 1993, George Heron, 24 at the time, was acquitted of Nikki’s murder by a jury at Leeds Crown Court in 1993.

Mr Justice Mitchell refused to allow certain tape recordings of Northumbria Police interviews with Mr Heron to be put before the jury. Consequently, the jury did not hear his admission on one recording that he killed Nikki.

A spokeswoman for Northumbria Police said: “At 3.17pm on Tuesday, July 14, police received a report of malicious communications from a person at an address in Sunderland. Police are currently carrying out investigations to establish the circumstances.”